edisoncarter's cheat device is now available for the UK version. You can download that here. You also may want to create a backup of your saved games just in case.

Unzip the archive to your memory card so the files go in PSP/SAVEDATA/ULUS10041S0 if you're installing the US version, PSP/SAVEDATA/ULES00151S0 for the UK version. This replaces the first save on the card.